<!DOCTYPE html>
<html>
<head>
<style type="text/css">

.hideradios input {
  display: none;
}

input:checked + label {
  background-color: yellow;
}

</style>

<script type="text/javascript">

function chooseSecondItems()
{
  document.getElementById("a2").checked = true;
  document.getElementById("b2").checked = true;
}

</script>
</head>

<body onload="chooseSecondItems();">

<div>
<div><input type="radio" name="a" id="a1"><label for="a1">radio #a1</label></div>
<div><input type="radio" name="a" id="a2"><label for="a2">radio #a2</label></div>
<div><input type="radio" name="a" id="a3"><label for="a3">radio #a3</label></div>
<div><input type="radio" name="a" id="a4" checked><label for="a4">radio #a4</label></div>
<div><input type="radio" name="a" id="a5"><label for="a5">radio #a5</label></div>
</div>

<div class="hideradios">
<div><input type="radio" name="b" id="b1"><label for="b1">radio #b1</label></div>
<div><input type="radio" name="b" id="b2"><label for="b2">radio #b2</label></div>
<div><input type="radio" name="b" id="b3"><label for="b3">radio #b3</label></div>
<div><input type="radio" name="b" id="b4" checked><label for="b4">radio #b4</label></div>
<div><input type="radio" name="b" id="b5"><label for="b5">radio #b5</label></div>
</div>

</body>
</html>
